1. Field of the Invention
The present invention relates to the field of lightweight, pocket-sized or portable scales and improvements thereto.
2. Description of Related Art
Portable balance beam scales with integrated carrying cases are well known in the art. A typical scale includes a fulcrum projecting from a base, which may double as the bottom half of the carrying case, as disclosed, for example, by U.S. Pat. No. 4,744,428 to KNOTTER et al. and U.S. Pat. No. 3,968,849 to DALE et al. The typical scale also includes a balance beam positioned across the fulcrum, with a substance holder or a load pan on one end and a graduated scale on the other end. The pan and the graduated scale are disposed on opposite sides of the fulcrum, so that a slidable weight (or weights) can be moved along the balance beam in order to balance the substance in the pan. When the load pan and the slidable weight are in equilibrium (i.e., the balance beam is balanced in a horizontal position), the weight of the substance in the load pan is equal to the number (or numbers) on the graduated scale next to which the slidable weights are positioned.
The prior art also includes a type of scale that incorporates a balance beam with a load pan on one side of a fulcrum and a weight pan on the other side of the fulcrum, as disclosed, for example, by U.S. Pat. No. 4,050,531 to ASHBROOK. In a portable scale having this design, a substance to be weighed is placed in the load pan and balancing weights of known mass are placed in the weight pan, until the pans are in equilibrium (i.e., the beam is horizontally balanced) across the fulcrum. The weight of the substance is then determined to be equal to the sum of the balancing weights.
To be effective, a portable scale must be balanced whenever the sliding weight is set in the zero position. Achieving an appropriate balance is problematic for a portable scale because the load pan must be as lightweight as possible to keep the overall weight of the scale at a minimum. Therefore, a measuring weight positioned on the balance beam opposite the load pan must be light weight as well, or the scale will not be in equilibrium when the load pan is empty and the measuring weight is in the zero position. However, the measuring weight must be heavy enough to accurately weigh substances up to several grams or ounces in order to have practical use.
One attempt to address the zero position balancing problem in the prior art was to place the bulk of the measuring weight in a vertical plane of the fulcrum whenever the measuring weight is in a zero position, as in KNOTTER et al. The positioning prevents the measuring weight from factoring into the balancing of the empty load pan. However, to position the measuring weight in the scale""s fulcrum requires a convoluted design of the measuring weight housing because, while the bulk of the weight is positioned in a plane of the fulcrum, an indicator of the weight must be adjacent to the zero position on the sliding scale. The additional material and the unorthodox design for the measuring weight housing increase manufacturing costs.
Another disadvantage common to the prior art is that the typical carrying case, being integrated with the scale operation (i.e., serving as the base of the scale), may undesirably interfere with the weighing process. For example, in KNOTTER et al., the carrying case has a bottom portion (i.e., the base) with relatively high sides in relation to the height of the fulcrum. Also, because the carrying case is designed to be compact, it defines an extremely close fit around the outer parameter of the load pan of the scales and around the end of the balance beam. The high sides combined with the close fit result in portions of the scale rubbing against the sides of the case during the weighting process, creating an inaccurate measurement. Furthermore, the high sides of the case interfere with the user attempting to place materials into the load pan or attempting to slide the movable weights along the balance beam. The interference with the user further enhances the chances of inaccurate measurement and increases the possibility of inadvertently spilling the contents of the load pan.
Also with respect to the carrying cases, the prior art includes cases that are substantially rectangular in shape, which has a number of drawbacks. For example, the scales are intended to be portable and inexpensive, so the more compact the carrying case the better. However, a substantially rectangular carrying case creates wasted, void spaces at the comer regions of the case corresponding to the more narrow portions of the enclosed scale. In particular, the carrying case must be wide enough to accommodate the load pan, which is much wider than the balance beam. Therefore, the portion of the carrying case housing only the balance beam region of the scale is significantly wider than the beam itself, resulting in unnecessary dimensional bulk to the case. Furthermore, the additional size of the case requires additional material and increased manufacturing costs, which are passed on to the customers.
The present invention is directed to a lightweight, portable scale and integrated carrying case, which addresses the problems existing in the prior art, discussed above.
An aspect of the present invention provides a portable scale that includes a fulcrum and a balance beam. The balance beam is pivotally mountable on the fulcrum and supports a load pan on one end and has a graduated scale extending from a zero position toward an opposite end of the balance beam. The fulcrum is positioned between the load pan and the zero position of the graduated scale. The portable scale further includes a dynamic weight and a stationary weight. The dynamic weight is movable along the balance beam from the zero position to the opposite end of the balance beam. The stationary weight is connected to the balance beam such that the fulcrum is positioned between the stationary weight and the dynamic weight.
The dynamic weight can include a fitting member, which has a channel configured to attach to the balance beam. The fitting member is thereby slidable along a guide channel of the balance beam. There is also a metal insert disposed within the fitting member such that the metal insert is centered on a central vertical axis of the fitting member. The stationary weight and the dynamic weight are removable and replaceable, which enables variations in a measurement range of the portable scale.
In another embodiment of the present invention, the portable scale includes a base, a pair of fulcrum posts projecting form the base, and a balance beam pivotally supported by the pair of fulcrum posts. The balance beam includes a load pan support member on one end and a graduated scale extending from a zero position toward an opposite end. The fulcrum posts are positioned between the load pan support member and the zero position of the graduated scale. The portable scale further includes a load pan that is pivotally supported by the load pan support member.
The portable scale also includes a dynamic weight member, movably mounted on the balance beam for movement along the graduated scale, and a stationary counter-weight. The stationary counter-weight balances against the dynamic weight when the dynamic weight is located at the zero position of the graduated scale. The dynamic weight can include a fitting member, which has a channel configured to attach to the balance beam. The fitting member is thereby slidable along a guide channel of the balance beam. There is also a metal insert disposed within the fitting member such that the metal insert is centered on a central vertical axis of the fitting member. No portion of the fitting member is located within a plane defined by the pair of fulcrum posts when the fitting member is positioned at the zero position of the graduated scale. The portable scale also includes a calibration weight, movable along a bottom side of the balance beam.
One aspect of the invention includes a carrying case. The carrying case has a top portion and a bottom portion, such that the top portion is closable onto the bottom portion. The bottom portion of the carrying case serves as the base of the portable scale. Also, the bottom portion of the carrying case has sides that are shorter than the pair of fulcrum posts projecting from the base. The top portion can be hingedly connected to the bottom portion of the carrying case.
In another aspect of the present invention, the portable scale includes a carrying case, having a tear-drop shape, and scale components. The carrying case includes a top portion and a bottom portion, such that the top portion is closable onto the bottom portion. The scale components include a fulcrum member projecting from the bottom portion of the carrying case and a balance beam pivotally supported by the fulcrum member. The balance beam supports a load pan on one end and a weight measuring device on an opposite end. The fulcrum is positioned between the load pan and the weight measuring device. The weight measuring device includes a dynamic weight member, which is movably mounted on the balance beam, and a graduated scale, which extends from a zero position of the balance beam toward an end of the balance beam opposite from the load pan. The dynamic weight member is slidably positioned on the graduated scale to balance against a substance contained in the load pan.
The load pan is positioned within an enlarged end of the tear-drop shaped carrying case and the balance beam is positioned within a narrowing end of the tear-drop shaped carrying case to provide efficient, economical storage of the scale components. The top portion of the carrying case is hingedly connected to the bottom portion. Also, the bottom portion of the carrying case has sides that are shorter than the pair of fulcrum posts projecting from the base.
The portable scale can also include a stationary counter-weight attached to the balance beam. The stationary counter-weight is located such that the fulcrum member is positioned between the stationary counter-weight and the weight measuring device. The stationary counter-weight balances against the dynamic weight member when the dynamic weight member is located at the zero position of the graduated scale.
Another aspect of the present invention provides a portable scale that includes a carrying case having a tear-drop shape and scale components. The carrying case includes a top portion and a bottom portion, such that the top portion is closable onto the bottom portion. The scale components include a pair of fulcrum posts projecting from the bottom portion of the carrying case and a balance beam pivotally supported by the pair of fulcrum posts. The balance beam includes a load pan support member on one end and a graduated scale extending from a zero position toward an opposite end. The pair of fulcrum posts is positioned between the load pan support member and the zero position of the graduated scale. The scale components further include a load pan pivotally supported by the said load pan support member and a dynamic weight member movably mounted on the balance beam for movement along the graduated scale.
The load pan is positioned within an enlarged end of the tear-drop shaped carrying case and the balance beam is positioned with a narrowing end of the tear-drop shaped carrying case to provide efficient, economical storage of the scale components. The top portion of the carrying case can be hingedly connected to the bottom portion. Also, the bottom portion of the carrying case has sides that are shorter than the pair of fulcrum posts projecting from the base.
The scale components also include a stationary counter-weight removably attached to the load pan support member. The stationary counter-weight balances against the dynamic weight member when the dynamic weight member is located at the zero position of the graduated scale. The scale components also include a calibration weight, movable along a bottom side of the balance beam.